Calculates a frequency table counting the number of times each pair of
states were observed in successive observation times. This can be a
useful way of summarising multi-state data.

Usage

1

Arguments

state

Observed states, assumed to be ordered by time
within each subject.

subject

Subject identification numbers corresponding to
state. If not given, all observations are assumed to be on
the same subject.

data

An optional data frame in which the variables represented
by subject and state can be found.

Details

If the data are intermittently observed (panel data) this table should
not be used to decide what transitions should be allowed in the
Q matrix, which works in continuous time. This function counts
the transitions between states over a time interval, not in real time.
There can be observed transitions between state r and s
over an interval even if q_{rs}=0, because the process may have
passed through one or more intermediate states in the middle of the
interval.

Value

A frequency table with starting states as rows and finishing states as
columns.